American Odds vs Decimal Odds: How to Read a Betting Line

American odds: the plus/minus system

American odds are written as either a positive or negative three-digit number, always relative to a $100 stake.

A negative number (e.g. -150) tells you how much you'd need to bet to win $100 profit. Betting $150 on a -150 favorite returns $100 profit plus your $150 stake back, for a $250 total payout.

A positive number (e.g. +130) tells you how much profit a $100 bet would win. A $100 bet on a +130 underdog returns $130 profit plus your $100 stake, for a $230 total payout.

The favorite always carries the negative number; the underdog always carries the positive number. When both sides are close to even, you'll sometimes see small numbers on both sides, like -110/-110 — more on why that matters below.

Decimal odds: the multiplier system

Decimal odds, standard in the UK and most of Europe, show your total payout per $1 (or £1) staked — stake included. A decimal odds of 2.50 means a $10 bet returns $25 total: $15 profit plus your original $10.

Decimal odds below 2.00 represent favorites (you get back less than double your stake); above 2.00 represents underdogs. A decimal of 1.67 is roughly equivalent to American -150; a decimal of 2.30 is roughly equivalent to American +130.

Converting between the two

You don't need to memorize a table. Two formulas cover it:

Negative American to decimal: (100 ÷ |American odds|) + 1
Example: -150 → (100 ÷ 150) + 1 = 1.67

Positive American to decimal: (American odds ÷ 100) + 1
Example: +130 → (130 ÷ 100) + 1 = 2.30

Most licensed sportsbooks let you switch the display format in your account settings, so in practice you rarely need to convert by hand — but knowing the math means you can sanity-check a line at a glance, on any site.

What the number is actually telling you: implied probability

Every odds format is a repackaged probability estimate. Decimal odds convert to implied probability with a simple formula: 1 ÷ decimal odds. A decimal of 1.67 implies a 59.9% chance of that outcome, according to the sportsbook's pricing. A decimal of 2.30 implies 43.5%.

Add the implied probabilities of both sides of a two-way market together and you'll typically get a number over 100% — often around 105-108%. That extra few percent is the sportsbook's built-in margin, sometimes called the "vig" or "hold." It's how sportsbooks make money regardless of outcome, and it's the mathematical reason no betting "system" can turn a structural long-run edge in your favor. You're not just betting against the other side — you're betting against a line that's priced to make the book money on both outcomes combined.

Why -110/-110 lines matter more than they look

A standard point-spread bet is often priced at -110 on both sides. Converting: -110 → decimal 1.91 → implied probability 52.4% per side → 104.8% combined. That 4.8% is the house's structural edge on a coin-flip-style bet. To break even betting -110 lines long-term, you'd need to win roughly 52.4% of your bets — not 50%. That gap is worth understanding before you bet, not after.

Reading a full betting line

A typical US sportsbook line combines three separate markets, and it helps to recognize each one:

Moneyline — a straight bet on who wins, no point spread involved. Priced in American or decimal odds as above.
Point spread — a handicap applied to the favorite so both sides are closer to a coin flip; usually priced near -110 on each side.
Total (over/under) — a bet on whether the combined score goes over or under a set number, also usually priced near -110.

Odds on all three shift constantly as money comes in and as the game clock moves, which is why the number you see at kickoff is rarely the number that opened.

Betting only where it's licensed

Sports betting legality is set at the state or national level, not decided by an operator's website. In the US, online sports betting is legal and regulated in most — not all — states; in the UK it's nationally regulated by the UK Gambling Commission. Only use operators licensed in your jurisdiction, and confirm your state or country's current legal status before signing up anywhere — it changes as legislatures act. We cover licensed operators in our Operator Reviews section.

You must be 21+ in the US or 18+ in the UK to bet legally. The odds above illustrate how sportsbooks price markets — they are not a prediction system, and no line-reading skill overcomes the built-in hold on every market. If gambling stops being fun, see our responsible gambling page.

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